<s>
Interactive	O
Systems	O
Corporation	O
(	O
styled	O
INTERACTIVE	O
Systems	O
Corporation	O
,	O
abbreviated	O
ISC	O
)	O
was	O
a	O
US-based	O
software	O
company	O
and	O
the	O
first	O
vendor	O
of	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
outside	O
AT&T	O
,	O
operating	O
from	O
Santa	O
Monica	O
,	O
California	O
.	O
</s>
<s>
D	O
.	O
advisor	O
to	O
Brian	O
Kernighan	O
,	O
one	O
of	O
Unix	B-Application
's	O
developers	O
at	O
AT&T	O
.	O
</s>
<s>
Weiner	O
was	O
joined	O
by	O
Heinz	O
Lycklama	O
,	O
also	O
a	O
veteran	O
of	O
AT&T	O
and	O
previously	O
the	O
author	O
of	O
a	O
Version	B-Operating_System
6	I-Operating_System
Unix	I-Operating_System
port	O
to	O
the	O
LSI-11	O
computer	O
.	O
</s>
<s>
which	O
sold	O
its	O
ISC	O
Unix	B-Application
operating	I-Application
system	I-Application
assets	O
to	O
Sun	O
Microsystems	O
on	O
September	O
26	O
,	O
1991	O
.	O
</s>
<s>
Several	O
former	O
ISC	O
staff	O
founded	O
Segue	O
Software	O
which	O
partnered	O
with	O
Lotus	O
Development	O
to	O
develop	O
the	O
Unix	B-Application
version	O
of	O
Lotus	B-Application
1-2-3	I-Application
and	O
with	O
Peter	O
Norton	O
Computing	O
to	O
develop	O
the	O
Unix	B-Application
version	O
of	O
the	O
Norton	O
Utilities	O
.	O
</s>
<s>
ISC	O
's	O
1977	O
offering	O
,	O
IS/1	O
,	O
was	O
a	O
Version	B-Operating_System
6	I-Operating_System
Unix	I-Operating_System
variant	O
enhanced	O
for	O
office	O
automation	O
running	O
on	O
the	O
PDP-11	B-Device
.	O
</s>
<s>
IS/3	O
and	O
IS/5	O
were	O
enhanced	O
versions	O
of	O
Unix	B-Operating_System
System	I-Operating_System
III	I-Operating_System
and	O
System	B-Operating_System
V	I-Operating_System
for	O
PDP-11	B-Device
and	O
VAX	B-Device
.	O
</s>
<s>
ISC	O
Unix	B-Application
ports	O
to	O
the	O
IBM	B-Device
PC	I-Device
included	O
a	O
variant	O
of	O
System	B-Operating_System
III	I-Operating_System
,	O
developed	O
under	O
contract	O
to	O
IBM	O
,	O
known	O
as	O
PC/IX	O
(	O
Personal	O
Computer	O
Interactive	O
eXecutive	O
,	O
also	O
abbreviated	O
PC-IX	O
)	O
,	O
with	O
later	O
versions	O
branded	O
386/ix	O
and	O
finally	O
INTERACTIVE	B-Operating_System
UNIX	I-Operating_System
System	O
V/386	O
(	O
based	O
on	O
System	B-Operating_System
V	I-Operating_System
Release	O
3.2	O
)	O
.	O
</s>
<s>
ISC	O
was	O
T	O
's	O
"	O
Principal	O
Publisher	O
"	O
for	O
System	B-Operating_System
V.4	I-Operating_System
on	O
the	O
Intel	O
platform	O
.	O
</s>
<s>
ISC	O
was	O
also	O
involved	O
in	O
the	O
development	O
of	O
VM/IX	O
(	O
Unix	B-Application
as	O
a	O
guest	O
OS	O
in	O
VM/370	B-Application
)	O
and	O
enhancements	O
to	O
IX/370	O
(	O
a	O
TSS/370	B-Application
-based	O
Unix	B-Application
system	I-Application
that	O
IBM	O
originally	O
developed	O
jointly	O
with	O
AT&T	O
ca	O
.	O
</s>
<s>
They	O
also	O
developed	O
the	O
AIX	B-Application
1.0	I-Application
(	O
Advanced	B-Application
Interactive	I-Application
eXecutive	I-Application
)	O
for	O
the	O
IBM	B-Device
RT	I-Device
PC	I-Device
,	O
again	O
under	O
contract	O
to	O
IBM	O
,	O
although	O
IBM	O
awarded	O
the	O
development	O
contract	O
for	O
AIX	B-Application
version	O
2	O
of	O
AIX/386	O
and	O
AIX/370	O
to	O
the	O
competing	O
Locus	O
Computing	O
Corporation	O
.	O
</s>
<s>
Although	O
observers	O
in	O
the	O
early	O
1980s	O
expected	O
that	O
IBM	O
would	O
choose	O
Microsoft	B-Application
Xenix	I-Application
or	O
a	O
version	O
from	O
AT&T	O
Corporation	O
as	O
the	O
Unix	B-Application
for	O
its	O
microcomputer	O
,	O
PC/IX	O
was	O
the	O
first	O
Unix	B-Application
implementation	O
for	O
the	O
IBM	B-Device
PC	I-Device
XT	O
available	O
directly	O
from	O
IBM	O
.	O
</s>
<s>
According	O
to	O
Bob	O
Blake	O
,	O
the	O
PC/IX	O
product	O
manager	O
for	O
IBM	O
,	O
their	O
"	O
primary	O
objective	O
was	O
to	O
make	O
a	O
credible	O
Unix	B-Application
system	I-Application
-	O
 [ ... ] 	O
not	O
try	O
to	O
'	O
IBM-ize	O
'	O
the	O
product	O
.	O
</s>
<s>
PC-IX	O
is	O
System	B-Operating_System
III	I-Operating_System
Unix.	O
"	O
</s>
<s>
PC/IX	O
was	O
not	O
,	O
however	O
,	O
the	O
first	O
Unix	B-Application
port	O
to	O
the	O
XT	O
:	O
Venix/86	B-Operating_System
preceded	O
PC/IX	O
by	O
about	O
a	O
year	O
,	O
although	O
it	O
was	O
based	O
on	O
the	O
older	O
Version	B-Operating_System
7	I-Operating_System
Unix	I-Operating_System
.	O
</s>
<s>
INed	O
offered	O
multiple	O
windows	O
and	O
context-sensitive	O
help	O
,	O
paragraph	O
justification	O
and	O
margin	O
changes	O
,	O
although	O
it	O
was	O
not	O
a	O
fully	O
fledged	O
word	B-General_Concept
processor	I-General_Concept
.	O
</s>
<s>
PC/IX	O
omitted	O
the	O
System	B-Operating_System
III	I-Operating_System
FORTRAN	B-Application
compiler	O
and	O
the	O
tar	B-Application
file	I-Application
archiver	O
,	O
and	O
did	O
not	O
add	O
BSD	B-Operating_System
tools	O
like	O
vi	B-Application
or	O
the	O
C	B-Operating_System
shell	I-Operating_System
.	O
</s>
<s>
One	O
reason	O
for	O
not	O
porting	O
these	O
was	O
that	O
in	O
PC/IX	O
,	O
individual	O
applications	O
were	O
limited	O
to	O
a	O
single	O
segment	O
of	O
64	O
kB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
To	O
achieve	O
good	O
filesystem	O
performance	O
,	O
PC/IX	O
addressed	O
the	O
XT	O
hard	O
drive	O
directly	O
,	O
rather	O
than	O
doing	O
this	O
through	O
the	O
BIOS	B-Operating_System
,	O
which	O
gave	O
it	O
a	O
significant	O
speed	O
advantage	O
compared	O
to	O
MS-DOS	O
.	O
</s>
<s>
PC/IX	O
was	O
not	O
a	O
commercial	O
success	O
although	O
BYTE	O
in	O
August	O
1984	O
described	O
it	O
as	O
"	O
a	O
complete	O
,	O
usable	O
single-user	O
implementation	O
that	O
does	O
what	O
can	O
be	O
done	O
with	O
the	O
8088	O
"	O
,	O
noting	O
that	O
PC/IX	O
on	O
the	O
PC	O
outperformed	O
Venix	B-Operating_System
on	O
the	O
PDP-11/23	B-Device
.	O
</s>
<s>
Later	O
versions	O
were	O
termed	O
INTERACTIVE	B-Operating_System
UNIX	I-Operating_System
System	O
V/386	O
and	O
based	O
on	O
System	B-Operating_System
V	I-Operating_System
3.2	O
,	O
though	O
with	O
elements	O
of	O
BSD	B-Operating_System
added	O
.	O
</s>
<s>
Its	O
SVR3.2	O
kernel	O
meant	O
diminished	O
compatibility	O
with	O
other	O
Unix	B-Application
ports	O
in	O
the	O
early	O
nineties	O
,	O
but	O
the	O
INTERACTIVE	B-Operating_System
UNIX	I-Operating_System
System	O
was	O
praised	O
by	O
a	O
PC	O
Magazine	O
reviewer	O
for	O
its	O
stability	O
.	O
</s>
<s>
After	O
its	O
acquisition	O
of	O
Interactive	O
,	O
Sun	O
Microsystems	O
continued	O
to	O
maintain	O
INTERACTIVE	B-Operating_System
UNIX	I-Operating_System
System	O
,	O
offering	O
it	O
as	O
a	O
low-end	O
alternative	O
to	O
its	O
System	O
V.4-based	O
Solaris	B-Application
,	O
even	O
when	O
the	O
latter	O
had	O
been	O
ported	O
to	O
x86-based	O
desktop	O
machines	O
.	O
</s>
<s>
Until	O
version	O
ISA	O
3.0.1	O
,	O
INTERACTIVE	B-Operating_System
UNIX	I-Operating_System
System	O
supported	O
only	O
16MB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
In	O
the	O
next	O
versions	O
,	O
it	O
supported	O
256MB	O
RAM	B-Architecture
and	O
the	O
PCI	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
EISA	B-Device
versions	O
always	O
supported	O
256MB	O
RAM	B-Architecture
.	O
</s>
